TRUDEAU: And at random times throughout the day, a mood map pops up on the cell phone.

Dr. MORRIS: And people drag a little red dot around that screen with their finger to indicate their current mood. And based on your mood, the phone offers therapeutic exercises, and these range from breathing visualizations...

TRUDEAU: Where a blue circle slowly expands and contracts, to more literal advice such as useful tips for disengaging from a stressful situation. Also, patient and therapist can later on look at the whole week of mood data to better understand what's linked to bad and good feelings.

Dr. MORRIS: How does my mood vary over the course of the day? How does it vary depending on who I'm with or what I ate?

TRUDEAU: Or how much I slept or exercised. So far, 60 people have tried the mobile therapy app.

Dr. MORRIS: And everyone who used it described new insights about their emotional variability.

TRUDEAU: Mobile apps are being used in Australia and Europe as well.

Mr. ALAN DELAHUNTY (Psychologist and Family Therapist, Health Service Executive-West): My name is Alan Delahunty. I'm a senior psychologist and family therapist with the Irish Health System.

TRUDEAU: Treating teens with depression who are being asked to chart their moods throughout the day. But Delahunty says teens especially balk at doing the paper charting. So researchers at Trinity College in Dublin developed a cell phone app being tested now by about 20 therapists throughout Ireland including Delahunty.

Mr. DELAHUNTY: From a clinical point of view, I found it a huge improvement over the pen and paper technique.

TRUDEAU: His young patients love the app, rarely missing doing their daily charting. And when they come into therapy...

Mr. DELAHUNTY: You get a complete printout of their mood, their energy level, their sleep patterns, and any comments they've made over the week or two. And then you can put that down on the table in front of you, and use it to discuss the therapy with the young person.

Professor JUDY CALLAN (Researcher, University of Pittsburgh): My name is Judy Callan.

TRUDEAU: From University of Pittsburgh. Callan is developing an app with colleagues at Carnegie Mellon for severely depressed adults. The app progresses as the patient progresses.

Prof. CALLAN: Say a patient just starts therapy and they're really depressed. And they can hardly get out of bed. One of their homework assignments might be to, each day, just make your bed.

TRUDEAU: And then, once the patient accomplishes this, the guidance on the app will change, expanding the hour-a-week therapy session almost into a mobile therapist 24/7.

Dr. DIMITRI PERIVOLIOTIS (Psychologist, University of Pennsylvania): My name is Dimitri Perivoliotis.